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Math Help - Derivatives chain rule/velocity

  1. #1
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    Derivatives chain rule/velocity

    I need to check my answers on part a, and see what's wrong on b. Also, what units do i use?

    An abnormal projectile is shot in the air, so that after t seconds, its height in feet is s(t)=14ln(-cos(\frac{x}{2}+1.67))+34
    a) find the velocity at times 0 and 5
    b) When is it highest? When does it land?

    my answers:
    I have the derivative as -7tan(/frac{x}{2}+1.67)
    a) @t=0, 70.33 (units?)
    @t=5, -11.6 (units?)

    b) I wasn't totally sure how to do it, so I set the derivative equal to 0. I thought that that should give me the max height, but I came out with -3.34, which is obviously wrong. Did i make a math error or should I not have set it equal to 0? please help!
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  2. #2
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    my bad:

    I have the derivative as [tex]-7tan(\frac{x}{2}+1.67)[\math]
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  3. #3
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    my bad again:

    I have the derivative as -7tan(/frac{x}{2})
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  4. #4
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    WTF? not working

    -7tan(\frac{x}{2}+1.67)
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